This invention relates generally to switching systems and, in particular, to the switching of data.
Local area networks (LAN) function by a network port transmitting a packet onto the LAN and determining if a collision occurred. As transmission rates increase the packet lengths decreases time wise. In addition, the geographical area that the LAN can cover also decreases since the interval for detecting collisions decreases as packet length shrinks in time. The network is limited to the distance at which all ports can still detect a collision during the packet transient time, and is limited in data throughput to less than the link rate. However, all of the LANs interconnected have the same restrictions with respect to transmission rates and geographical area.
Bridges or gateways between LANs eliminate the need for all ports within the combined LANs to detect a collision during a packet transient time. However, bridges and/or gateways require that the packet be stored internally to the bridge or gateway before it is transferred from one LAN to another LAN. In addition, the complexity of the protocol utilized by the network ports is increased since the network port has no simple mechanism for determining whether the packet reached the destination port. On a single LAN, this simple detection of whether the packet reached the destination is based on whether a collision occurred or not.
The foregoing problems are solved, and a technical advance is achieved by an apparatus and method in which local area networks are dynamically connected to one another by a switching system only when there is a packet to be exchanged between the two local area networks, otherwise the local area networks operate as separate and independent local area networks. Advantageously, the switching system can concurrently interconnect multi-pairs of local area networks together. Advantageously, the overall capacity of the local area networks interconnected via the switching system is increased since the local area networks operate free of other local area networks except when directly exchanging packets with another local area network.
Advantageously, the switching system comprises a space switching unit and switch interface units with each switch interface unit interconnecting an individual local area network to the space switching unit. When a first switch interface unit receives a packet from a connected local area network destined for another local area network, the first switch interface unit establishes a first unilateral path from the other local area network via a second switch interface unit connected to the other local area network and the space switching unit to the first switch interface unit. The first switch interface unit determines if the other local area network is idle via the first unilateral path. If the other local area network is idle, the first switch interface unit establishes a second unilateral path from the connected local area network to the other local area network via the space switching unit and the first and second switch interface units so that the packet from the connected local area network can be transmitted to the other local area network. The first switch interface unit remove both unilateral paths after transmission of the packet. If the first switch interface unit determines that the other local area network is busy via first unilateral path, the first switch interface unit generates a collision message to the connected local area network.